The invention relates to novel urea compounds. In particular it relates to novel urea compounds of the formula R.sub.1 CH.sub.2 S(CH.sub.2).sub.2 NHCONHR.sub.2, which are inhibitors of H-2 histamine receptors and, therefore, useful as anti-ulcer agents.
It has long been postulated that many of the physiologically active substances within the animal body, in the course of their activity, combine with certain specific sites known as receptors. Histamine is a compound which is believed to act in such a way, but since the actions of histamine fall into more than one type, it is believed that there is more than one type of histamine receptor. The type of action of histamine which is blocked by drugs commonly called "antihistamines" (of which mepyramine is a typical example) is believed to involve a receptor which has been designated as H-1. A further group of substances has been described by Black et al. (Nature 1974, 236, 385) which are distinguished by the fact that they act at histamine receptors other than the H-1 receptor and these receptors have been designated as H-2 receptors. This latter group of substances, to certain of which the present invention relates, are thus of utility in inhibiting certain actions of histamines which are not inhibited by the above-mentioned "antihistamines;" that is, they are H-2 histamine receptor inhibitors. Inhibitors of H-2 histamine receptors, which are also referred to as histamine H-2 antagonists, are useful, for example, as inhibitors of gastric acid secretion. The histamine H-2 antagonists of this invention may also be of utility as inhibitors of certain actions of gastrin. In the treatment of certain conditions, for example inflammation and in inhibiting the actions of histamine, H-1 and H-2 antagonists are useful.